1. Field
This disclosure generally relates to processes for fabricating curved composite structures, and deals more particularly with a method of fabricating composite structures such as stiffeners having compound curves using composite prepreg tape.
2. Background
During layup of prepreg plies over a tool, it is sometimes necessary to closely conform the plies to curves, contours and/or features of the tool in order to assure that the fibers follow the load path, and the layup is dimensionally accurate and substantially free of voids, wrinkling and/or buckling. Known techniques for conforming plies to curved tool surfaces involve darting, cutting and/or splitting the plies during the layup process, and/or extensive hand sweeping to conform a ply to contoured tool surfaces. These techniques can be time consuming and/or may not result in a cured part having the desired mechanical strength. Another solution to the problem involves incrementally steering relatively narrow slit prepreg tape onto a contoured tool in order to form curved plies. However the use of slit tape may increase material costs and reduce production rates since laying down slit tape may be more time consuming.
Accordingly, there is a need for a method of laying up and forming curved composite plies, especially 0 degree plies, using substantially straight unidirectional prepreg tape. There is also a need for a method of laying up and forming curved zero degree plies that avoids the need for incrementally steering individual strips of slit tape around a curved tool.